Pollution
Pollution is the addition of something to an ecosystem that damages the living organisms in it. Water pollution Water pollution by fertilisers causes eutrophication, while untreated sewage can always cause this problem. However, sewage can also cause disease problems, with human urine and faeces transmitting diseases such as cholera and typhoid. People catch these water transmitted diseases by swimming in, drinking or eating food that has come into contact with contaminating water. See also sewage treatment Water pollution by inorganic waste One inorganic water polluter is mercury. This is highly toxic, and can escape into water from factories. Air pollution When fossil fuels are burnt, carbon dioxide and sulphur dioxide are released into the atmosphere. Sulphur dioxide is an irritant, meaning it can trigger an asthma attack. it also gets into plants through the stomata, killing the cells and often eventually the whole plant. theres a pollution in bangladesh called Sushoma, it killed many people See also: acid rain Pollution by pesticides and herbicides Pesticides are chemicals which kill pests, while herbicides are chemicals used to kill weeds. Benefits of pesticides *Pesticides reduce crop losses *Pesticides control the spread of diseases spread by insects: pesticides control the population of mosquitos, reducing massively the number of people catching malaria *Pesticides have increased food production (in LEDCs it is estimated that 1/3 of crops are lost to pests, and cotton production is closer to 50%) Problems with pesticides *Some pesticides may remain in the environment, such as DDT. It remained in the food chain, and thus became more concentrated as it was passed along. Carnivores had so much DDT in their systems they died. DDT is now banned. *Pesticides may end up in human food, as pesticide residues. This means people could be poisoned *Pesticides can be absorbed through the skin, and poisoned if not wearing the correct protective clothing *Insects and weeds may become resistant. This is similar to how bacteria become resistant to antibodies. *Insecticides may kill helpful insects as well as harmful ones. These are non-specific insecticides. The Future Many farmers are turning over to biological control, where natural predators are used to keep a pest's population under control Nuclear fallout Ionizing radiation, including alpha, beta and gamma rays can damage DNA. This can lead to cancer or birth defects. Radiation sickness can also occur when the body is exposed to large quantities of radiation. This can cause death. There is always ionizing radiation, from rocks in the earth and from the sun's cosmic rays. This is background radiation, however it is not great enough to cause damage. Nuclear reactions, from either nuclear fission or nuclear fusion can give of great amounts of radiation. Therefore nuclear reactions take place in nuclear power stations, when little/no radiation can escape. However, if an accident happens, such as at Chernobyl, lots of radioactive substances can be released into the air. This is nuclear fallout. Nuclear bombs also cause massive amounts of this nuclear fallout. poopPorrrrrrrrrrrrrrrllution by non-biodegradable plastics Biodegradable substances, such as sewage will be broken down my microorganisms over time. However, non-biodegradable substances will remain in the environment for ever if thrown away. Disposal of non-biodegradable plastics is difficult: burial means they remain in the soil for years, burning gives of toxic gases. One of the best ideas is recycling, for example PET can be recycled. This reduces plastic pollution. Category: Biology